IPPOOL(5) IPPOOL(5)
NAME
ippool, ippool.conf - IP Pool file format
DESCRIPTION
The file ippool.conf is used with ippool(8) to configure address pools
for use with ipnat(8) and ipf(8).
There are four different types of address pools that can be configured
through ippool.conf. The various types are presented below with a brief
description of how they are used:
dstlist
destination list - is a collection of IP addresses with an
optional network interface name that can be used with either re-
direct (rdr) rules in ipnat.conf(5) or as the destination in
ipf.conf(5) for policy based routing.
group-map
group maps - support the srcgrpmap and dstgrpmap call functions
in ipf.conf(5) by providing a list of addresses or networks rule
group numbers to start processing them with.
hash
hash tables - provide the means for performing a very efficient
lookup address or network when there is expected to be only one
exact match. These are best used with more static sets of
addresses so they can be sized optimally.
pool
address pools - are an alternative to hash tables that can per-
form just as well in most circumstances. In addition, the
address pools allow for heirarchical matching, so it is possible
to define a subnet as matching but then exclude specific
addresses from it.
Evolving Configuration
Over time the configuration syntax used by ippool.conf(5) has evolved.
Originally the syntax used was more verbose about what a particular
value was being used for, for example:
table role = ipf type = tree number = 100
{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
The IP pool configuration file is used for defining a single object
that contains a reference to multiple IP address/netmask pairs. A pool
may consist of a mixture of netmask sizes, from 0 to 32.
At this point in time, only IPv4 addressing is supported.
OVERVIEW
The IP pool configuration file provides for defining two different
mechanisms for improving speed in matching IP addresses with rules.
The first, table , defines a lookup table to provide a single reference
in a filter rule to multiple targets and the second, group-map , pro-
vides a mechanism to target multiple groups from a single filter line.
The group-map command can only be used with filter rules that use the
call command to invoke either fr_srcgrpmap or fr_dstgrpmap , to use the
source or destination address, respectively, for determining which fil-
ter group to jump to next for continuation of filter packet processing.
POOL TYPES
Two storage formats are provided: hash tables and tree structure. The
hash table is intended for use with objects all containing the same
netmask or a few different sized netmasks of non-overlapping address
space and the tree is designed for being able to support exceptions to
a covering mask, in addition to normal searching as you would do with a
table. It is not possible to use the tree data storage type with
group-map configuration entries.
POOL ROLES
When a pool is defined in the configuration file, it must have an asso-
ciated role. At present the only supported role is ipf. Future devel-
opment will see futher expansion of their use by other sections of
IPFilter code.
EXAMPLES
The following examples show how the pool configuration file is used
with the ipf configuration file to enhance the ability for the ipf con-
figuration file to be succinct in meaning.
1 The first example shows how a filter rule makes reference to a
specific pool for matching of the source address.
pool ipf/tree (name "100";)
{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
Both of the above examples produce the same configuration in the kernel
for use with ipf.conf(5).
Newer options for use in ippool.conf(5) will only be offered in the new
configuration syntax and all output using "ippool -l" will also be in
the new configuration syntax.
IPFilter devices and pools
To cater to different administration styles, ipool.conf(5) allows you
to tie a pool to a specific role in IPFilter. The recognised role names
are:
ipf
pools defined for role "ipf" are available for use with all
rules that are found in ipf.conf(5) except for auth rules.
nat
pools defined for role "nat" are available for use with all
rules that are found in ipnat.conf(5).
auth
pools defined for role "auth" are available only for use with
"auth" rules that are found in ipf.conf(5)
all
pools that are defined for the "all" role are available to all
types of rules, be they NAT rules in ipnat.conf(5) or firewall
rules in ipf.conf(5).
Address Pools
An address pool can be used in ipf.conf(5) and ipnat.conf(5) for match-
ing the source or destination address of packets. They can be referred
to either by name or number and can hold an arbitrary number of address
patterns to match.
An address pool is considered to be a "tree type". In the older config-
uration style, it was necessary to have "type=tree" in ippool.conf(5).
In the new style configuration, it follows the IPFilter device with
which the pool is being configured. Now it is the default if left out.
For convenience, both IPv4 and IPv6 addresses can be stored in the same
address pool. It should go without saying that either type of packet
can only ever match an entry in a pool that is of the same address fam-
ily.
The address pool searches the list of addresses configured for the best
match. The "best match" is considered to be the match that has the
highest number of bits set in the mask. Thus if both 2.2.0.0/16 and
2.2.2.0/24 are present in an address pool, the addres 2.2.2.1 will
match 2.2.2.0/24 and 2.2.1.1 will match 2.2.0.0/16. The reason for this
is to allow exceptions to be added through the use of negative match-
ing. In the following example, the pool contains "2.2.0.0/16" and
"!2.2.2.0/24", meaning that all packets that match 2.2.0.0/16, except
those that match 2.2.2.0/24, will be considered as a match for this
pool.
table role = ipf type = tree number = 100
{ 1.1.1.1/32; 2.2.0.0/16; !2.2.2.0/24; ef00::5/128; };
The prior example is the older file format. The declaration that
defines the pool itself has been updated and can now be expressed as
below:
pool ipf/tree (name "100";)
{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
If the role and table type are left out, such as in the exmaple below,
the default is to make the table available to all aspects of IPFilter
and for the storage type to be "tree".
pool (name "100";)
{ 1.1.1.1/32; !2.2.0.0/16; 2.2.2.0/24; ef00::5/128; };
For the sake of clarity and to aid in managing large numbers of
addresses inside address pools, it is possible to specify a location to
load the addresses from. To do this simply use a "file://" URL where
you would specify an actual IP address.
pool ipf/tree (name rfc1918;) { file:///etc/ipf/rfc1918; };
The contents of the file might look something like this:
# RFC 1918 networks
10.0.0.0/8
!127.0.0.0/8
172.16.0.0/12
192.168.0.0/24
In this example, the inclusion of the line "!127.0.0.0/8" is, strictly
speaking not correct and serves only as an example to show that nega-
tive matching is also supported in this file.
Another format that ippool(8) recognises for input from a file is that
from whois servers. In the following example, output from a query to a
WHOIS server for information about which networks are associated with
the name "microsoft" has been saved in a file named "ms-networks".
There is no need to modify the output from the whois server, so using
either the whois command or dumping data directly from it over a TCP
connection works perfectly file as input.
pool ipf/tree (name microsoft;) { whois file "/etc/ipf/ms-networks"; };
And to then block all packets to/from networks defined in that file, a
rule like this might be used:
block in from pool/microsoft to any
Note that there are limitations on the output returned by whois servers
so be aware that their output may not be 100% perfect for your goal.
Destination Lists
Destination lists are provided for use primarily with NAT redirect
rules (rdr). Their purpose is to allow more sophisticated methods of
selecting which host to send traffic to next than the simple round-
robin technique that is present with with "round-robin" rules in
ipnat.conf(5).
When building a list of hosts to use as a redirection list, it is nec-
essary to list each host to be used explicitly. Expressing a collection
of hosts as a range or a subnet is not supported. With each address it
is also possible to specify a network interface name. The network
interface name is ignored by NAT when using destination lists. The
network itnerface name is currently only used with policy based routing
(use of "to"/"dup-to" in ipf.conf(5)).
Unlike the other directives that can be expressed in this file, desti-
nation lists must be written using the new configuration syntax. Each
destination list must have a name associated with it and a next hop
selection policy. Some policies have further options. The currently
available selection policies are:
round-robin
steps through the list of hosts configured with the destination
list one by one
random
the next hop is chosen by random selection from the list avail-
able
src-hash
a hash is made of the source address components of the packet
(address and port number) and this is used to select which next
hop address is used
dst-hash
a hash is made of the destination address components of the
packet (address and port number) and this is used to select
which next hop address is used
hash
a hash is made of all the address components in the packet
(addresses and port numbers) and this is used to select which
next hop address is used
weighted
selecting a weighted policy for destination selection needs fur-
ther clarification as to what type of weighted selection will be
used. The sub-options to a weighted policy are:
connection
the host that has received the least number of connec-
tions is selected to be the next hop. When all hosts have
the same connection count, the last one used will be the
next address selected.
The first example here shows 4 destinations that are used with a round-
robin selection policy.
pool nat/dstlist (name servers; policy round-robin;)
{ 1.1.1.2; 1.1.1.4; 1.1.1.5; 1.1.1.9; };
In the following example, the destination is chosen by whichever has
had the least number of connections. By placing the interface name with
each address and saying "all/dstlist", the destination list can be used
with both ipnat.conf(5) and ipf.conf(5).
pool all/dstlist (name servers; policy weighted connection;)
{ bge0:1.1.1.2; bge0:1.1.1.4; bge1:1.1.1.5; bge1:1.1.1.9; };
Group maps
Group maps are provided to allow more efficient processing of packets
where there are a larger number of subnets and groups of rules for
those subnets. Group maps are used with "call" rules in ipf.conf(5)
that use the "srcgrpmap" and "dstgrpmap" functions.
A group map declaration must mention which group is the default group
for all matching addresses to be applied to. Then inside the list of
addresses and networks for the group, each one may optionally have a
group number associated with it. A simple example like this, where the
first two entries would map to group 2020 but 5.0.0.0/8 sends rule pro-
cessing to group 2040.
group-map out role = ipf number = 2010 group = 2020
{ 2.2.2.2/32; 4.4.0.0/16; 5.0.0.0/8, group = 2040; };
An example that outlines the real purpose of group maps is below, where
each one of the 12 subnets is mapped to a different group number. This
might be because each subnet has its own policy and rather than write a
list of twelve rules in ipf.conf(5) that match the subnet and branch
off with a head statement, a single rule can be used with this group
map to achieve the same result.
group-map ( name "2010"; in; )
{ 192.168.1.0/24, group = 10010; 192.168.2.0/24, group = 10020;
192.168.3.0/24, group = 10030; 192.168.4.0/24, group = 10040;
192.168.5.0/24, group = 10050; 192.168.6.0/24, group = 10060;
192.168.7.0/24, group = 10070; 192.168.8.0/24, group = 10080;
192.168.9.0/24, group = 10090; 192.168.10.0/24, group = 10100;
192.168.11.0/24, group = 10110; 192.168.12.0/24, group = 10120;
};
The limitation with group maps is that only the source address or the
destination address can be used to map the packet to the starting
group, not both, in your ipf.conf(5) file.
Hash Tables
The hash table is operationally similar to the address pool. It is used
as a store for a collection of address to match on, saving the need to
write a lengthy list of rules. As with address pools, searching will
attempt to find the best match - an address specification with the
largest contiguous netmask.
Hash tables are best used where the list of addresses, subnets and net-
works is relatively static, which is something of a contrast to the
address pool that can work with either static or changing address list
sizes.
Further work is still needed to have IPFilter correctly size and tune
the hash table to optimise searching. The goal is to allow for small to
medium sized tables to achieve close to O(1) for either a positive or
negative match, in contrast to the address pool, which is O(logn).
The following two examples build the same table in the kernel, using
the old configuration format (first) and the new one (second).
table role=all type=hash name=servers size=5
{ 1.1.1.2/32; 1.1.1.3/32; 11.23.44.66/32; };
pool all/hash (name servers; size 5;)
{ 1.1.1.2; 1.1.1.3; 11.23.44.66; };
FILES
/dev/iplookup
/etc/ippool.conf
/etc/hosts
SEE ALSOippool(8), hosts(5), ipf(5), ipf(8), ipnat(8)IPPOOL(5)

You can also request any man page by name and (optionally) by section:

Command:

Section:

Architecture:

Collection:

Use the DEFAULT collection to view manual pages
for third-party software.